In recent years, there is a demand for miniaturization of a lens barrel, in addition to high performance and high function. Seeking high performance results in an increase in the size of a lens and a driving portion for driving e.g. the lens. As a result, the size of the lens barrel is increased, which is against the demand for miniaturization. Seeking miniaturization of a lens barrel results in a decrease in the clearance between components, which makes it difficult to assemble the lens barrel.
Generally, a lens barrel is internally provided with electrical components, and the electrical components and a camera-body-side circuit board are electrically connected via a flexible printed circuit board (hereinafter, called as “FPC”). Since miniaturization of a lens barrel results in a decrease in the space for installing an FPC, disposing the FPC at an inappropriate position may cause interference between the FPC and a driving member during use of a camera, which may damage the FPC. Further, disposing the FPC at an inappropriate position may cause tearing of the FPC at the time of assembling the lens barrel, which may damage the FPC and result in operation failure of the lens barrel.
In particular, in most of the cases, a lens barrel incorporated in an exchange lens for a single-lens reflex camera is provided with an inner focus system, a lens system loaded with a motor, and a shake correction mechanism. In particular, in the case where an inner-focus system is employed in a large aperture lens, movable members are disposed on the image side. Consequently, electrical components are disposed on the object side, which increases the length of the FPC to be electrically connected to a camera-body-side component. Further, considering the connection workability between the FPC, and a lens mount incorporated with an electrical contact with the camera-body-side component, it is necessary to secure a sufficiently long length for the FPC, in view of the need of pulling out the FPC from the lens barrel. The disposed position of the FPC is important for accommodating the FPC of such a long size in the lens barrel, while avoiding interference with the movable members. In other words, it is required to dispose an FPC at such a position that secures easy assembling in a limited space.
As shown in FIG. 6, patent literature 1 discloses a lens barrel comprising a fixed cylinder 2000, and an attachment base plate 3000 which is formed at a position facing a side wall of the fixed cylinder 2000, with an electronic component group 1000 being mounted on the fixed cylinder 2000 side, wherein an FPC is folded two times and accommodated in a space between the attachment base plate 3000 and the side wall of the fixed cylinder 2000.
As shown in FIG. 7, patent literature 2 discloses a lens barrel constructed in such a manner that a support plate 5400 which is slidably movable relative to an optical axis direction, and an electrical component 4200a provided on the lower side of the support plate 5400 are connected to each other by an FPC 6500. In patent literature 2, the FPC 6500 has an end thereof mounted on the upper surface of the support plate 5400, is folded toward the lower side so that the FPC 6500 faces the lower surface of the support plate 5400, and then, is bent in a direction orthogonal to the support plate 5400, with the other end thereof being connected to the electrical component 4200a. 
However, patent literature 1 merely discloses a technology that an FPC is folded two times to be accommodated, and fails to provide a countermeasure against contact between the FPC and the electronic component group 1000. Accordingly, the FPC may be damaged by the electronic component or by soldering for use in connecting the electronic component. Further, an erroneous operation may occur resulting from noise superimposed on an electrical signal. In the technology disclosed in patent literature 2, the FPC 6500 is attached to the upper surface of the support plate 5400, and is folded toward the lower side. Accordingly, a force may be exerted on the FPC 6500 in such a direction as to peel off the FPC 6500 from the support plate 5400. Long-time use of the lens barrel in such a condition may result in peeling off of the attachment portion of the FPC 6500, and interference with a member adjacent to the FPC 6500 at the time of operation, which may cause generation of abnormal sound or conduction failure.